OK, at least they are not claiming 10x increases in fuel economy anymore, it reduced to the more reasonable 5x, which is sorta believable, especially since most

OK, at least they are not claiming 10x increases in fuel economy anymore, it reduced to the more reasonable 5x, which is sorta believable, especially since most of the affordable jets are not using latest generations of jet engines. Let me guess: the catch is the high maintenance cost of the piston engine.